This invention relates to the reduction of solar radiation transmittance through existing glazing installations, more particularly, to the addition of a tinted or coated sheet of glass to an installed window so as to reduce glare and/or total solar energy transmittance.
A great majority of the buildings constructed over the years have been glazed with clear glass. But the popularization of air conditioning together with the rising costs of energy have made it desirable to limit the amount of solar radiation transmitted through glazing installations to amounts less than that transmitted by ordinary clear glass. Thus, in recent years, it has become more common to glaze new construction with glass that has been designed to absorb and/or reflect more radiation than ordinary clear glass, especially radiation in or near the infrared region of the spectrum. But to remove glazing from existing buildings and replace it with all new glass incurs prohibitive expenses in both materials and labor, and is very impractical on tall buildings glazed from the outside.
One currently commercially available means for reducing radiation transmittance through installed glazing takes the form of thin, tinted, plastic films that are applied to the inside surfaces of windows, an example of which may be seen in U.S. Pat. No. 3,891,486 to Willdorf. This approach, however, suffers from numerous drawbacks, chief among which are an appreciable reduction of optical fidelity, insufficient solar energy control, and a susceptibility to scratching which makes cleaning difficult. Air bubbles trapped between the film and the glass can also be troublesome.
The application of an additional pane of glass to an installed pane is not in itself new, such a concept having been shown in at least the following U.S. Pat. Nos.
1,777,432 -- C. F. Hogelund PA1 1,915,098 -- A. W. Kile PA1 1,945,742 -- W. P. Hilger PA1 2,098,127 -- W. P. Auger PA1 2,177,001 -- W. Owen PA1 2,436,037 -- W. A. Doney PA1 2,622,285 -- C. J. Roos PA1 2,780,845 -- G. G. Lyon PA1 3,299,591 -- H. Woelk PA1 3,573,149 -- W. J. Tibble et al.
Each of these patents is concerned solely with improving insulating properties by providing a spacer element so as to create an insulating airspace. None deal with the reduction of solar radiation transmittance. Furthermore, none of these patents discloses a sealing arrangement for the enclosed airspace that provides sufficient protection against moisture penetration and condensation in the airspace so as to make permanent architectural installation practical.